1. Field of the Invention
The present invention relates to a recording-material type determination apparatus, recording-material type determination method, and image forming apparatus such as a copier or laser printer which controls imaging conditions using the recording-material type determination apparatus.
2. Related Background Art
An image forming apparatus such as a copier or laser printer comprises a latent-image bearing member which bears a latent image, a developing apparatus which visualizes the latent image as a developer image (developed image) by applying developer to the latent-image bearing member, transferring means which transfers the developer image formed by the developing apparatus to recording material conveyed in a predetermined direction, and a fixing apparatus which fixes the developer image on the recording material by applying heat and pressure to the recording material under predetermined fixing conditions after the developer image has been transferred to the recording material by the transferring means.
Conventionally, such an image forming apparatus controls to set fixing conditions (e.g., fixing temperature and conveying speed of the recording paper passing through the fixing apparatus) according to user settings after the user sets a size and type (also called a paper type) of the recording paper, which is recording material, on a control panel or the like installed, for example, on the image forming apparatus main body.
Alternatively, an image forming apparatus incorporates a sensor for determining recording material and controls developing conditions, fixing conditions or transfer conditions variably according to the type of recording material.
In the latter case, in particular, Japanese Patent Application Laid-Open No. 11-27103, for example, proposes a technique for picking up a surface picture of recording material using a CCD sensor, converting it into fractal dimension information, and thereby detecting the surface flatness of the recording material.
However, the image forming apparatus has the following problems.
1) When calculations are performed using fractal dimensions, picture information is binarized according to a certain threshold and the number of black pixels is counted based on the binarized information. Then, the picture information is visualized roughly and binarized similarly and the number of black pixels is counted again based on the binarized information. This process is repeated several times, taking a very long calculation time.
Therefore, especially if surface flatness varies widely within one sheet of recording material, video images of a plurality of points on the recording material need to be detected. In such a case, it takes time to detect the surface flatness of the recording material, reducing the throughput (the number of prints per unit time) of the image forming apparatus
2) The calculation method, if implemented by a hardware circuit, will increase the scale of the circuit, reducing the cost-effectiveness of the image forming apparatus significantly.
3) Furthermore, if implemented by a software, the calculation method, which binarizes captured images and performs calculation, binarizes the resulting images and performs calculation, and so on, requires a memory (RAM) to buffer the captured images and the images resulting from calculations. Especially if a sensor with increased pixel counts is used to improve detection accuracy, the buffer memory will increase in size, reducing the cost-effectiveness of the image forming apparatus significantly.